CHM 101

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CHM 101
GAGE
FALL 1999
NAME __________________________________
SECTION
4225
EXAM 3
SHOW ALL WORK TO RECEIVE CREDIT FOR PROBLEMS
1.
Supply the most appropriate word, phrase, or value for each of the following statements:
(26)
a. term for solid matrix made of repeating unit cells
a._________________________
b. standard temperature in kelvins
b._________________________
c. crystal type that has high melting point but does not
conduct when melted
d. general term for a substance that reduces surface tension
c._________________________
d._________________________
e. value for standard molar volume
e._________________________
f. term for change from a solid to liquid
f._________________________
g. intermolecular forces between molecules of bromine
g._________________________
h. two factors that affect boiling point
h._________________________
________________________
i. example of a molecular crystal
i._________________________
j. two characteristics of a gas based on the Kinetic Molecular
Theory
j._________________________
_________________________
k. term for shapeless solid
2.
k.________________________
What mass of dintrogen oxide gas will occupy 3.8 liters at 980. mmHg and 29oC?
1
(9)
3.
Calculate the amount of energy transferred when 225 grams of water change from liquid
water at 0OC to 130OC.
(15)
O
sp.ht ice = 2.05 J/g$ C
Hvap = 2.25 kJ/g
sp.ht liquid = 4.18 J/g$OC
sp.ht steam = 2.10 J/g$OC
Hfus = 0.330 kJ/g
This process is:
exothermic
endothermic
(circle one)
4.
A gas sample has a volume of 550 mL at STP. What is its volume at 480 mmHg and
100oC?
(9)
5.
Complete the following chart.
Species
(9)
Molecular Geometry
(name only)
Polar or Non-Polar
Molecule?
NH2F
BH3
SeI6
2
Type of
Hybridization
6.
7.
Put the following sets of compounds in order from lowest to highest boiling point and
explain what factor(s) cause them to be in that order.
(8)
a.
CH4
H2O
NH3
_________________________________
b.
NF3
AsF3
SbF3
_________________________________
Answer any four of the following completely but briefly. You may answer a fifth one for
extra credit. If you answer more than 5 you must indicate which ones you wish to be
graded or only the first 5 in order will be read. Use the back of this paper to continue.
(24)
a.
Explain why water is a liquid at room temperature while H2S with a higher molar
mass is a gas.
b.
You subject a sample of a gas to high pressure and low temperature. When you
measure the volume of the gas it is higher than you predicted it should be.
Explain why this might happen.
c.
Explain why a substance will convert to a gas even though it means going to a
higher energy state.
d.
How can you change the boiling point of a liquid without adding anything? Why
does it work?
e.
Explain what happens when a gas in a rigid container is heated and why.
Consider what is happening at the particle level.
f.
Water is particularly efficient at cooling your body. Explain how and why.
g.
Sulfur dioxide with a molar mass of 64 g/mol is a gas at room temperature while
silicon dioxide with a molar mass of 60 g/mol is a solid with a very high melting
point. Explain why.
3
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